1. Field of the Invention
This invention relates in general to earth boring bits, and in particular to a rock bit having a quick change connection for use with an auger drilling machine.
2. Description of the Prior Art
Earth boring bits of the rolling cutter rock bit type are most frequently used for relatively deep small diameter holes. Conventional bits typically contain male threads for connection to the drill stem. A circulating fluid is pumped through the bit to wash cuttings from the borehole to the surface. The rotary rock bit drilling system combines the drilling and cuttings removal function into a continuous operation in which the drilling and cuttings removal by means of fluid circulation occur simultaneously and continuously.
Auger drilling machines normally are used for drilling relatively large diameter shallow holes for foundations, piers, and the like and conventionally use a helical flighted auger. Often the auger is supplemented by pilot bits attached to the bottom end. The auger normally has a square female box connection which connects to the bottom of a kelly. The female connection has no threads, is pinned to the kelly, and is axially releaseable. A circulation fluid is generally unnecessary since cuttings are collected on the auger, which is occassionally raised to the surface for dumping the cuttings. Thus, auger drilling is an intermittent, cyclical drilling system in which the drilling function is completely separated from the cuttings removal function, which is purely mechanical.
At times, for hard rock drilling, it is desirable to replace the auger with a rock bit while utilizing the same auger drilling machine. Since conventional rock bits contain a threaded male pin, a matching threaded female box had to be attached to the bottom of the kelly. The box was hollow so that fluid could be pumped through the bit to prevent packing of the cutter teeth with cuttings. The threaded coupling also requires the use of a break-out apparatus which is a cumbersome addition to an auger drilling machine.